The present invention relates to a method and devices for cleaning, decontaminating, deburring, or smoothing a work surface. More particularly, the present invention relates to a method whereby ice particulates are formed under pressure and transported by pressure flow to a nozzle which propels the same at high speeds for delivery to the work surface for cleaning, decontaminating, deburring, paint stripping, or smoothing.
In recent years there has been increasing interest in the use of ice blasting techniques to treat surfaces. For certain applications, ice blasting provides significant advantages over other abrasion techniques, such as chemical surface treatment, blasting with abrasive materials, hydro-blasting, or blasting with steam or dry ice. Ice blasting can be used to remove loose material, blips and burrs from production metal components and even softer materials. Because water in either frozen or liquid form is environmentally safe, ice blasting does not pose a waste disposal problem. Also, ice blasting is relatively inexpensive, as compared to other methods for cleaning and treating a surface.
Because of these apparent advantages, ice blasting has generated significant commercial interest which has led to the development of a variety of devices designed to deliver a spray containing ice particulates for performing surface treatment procedures. Typically, these ice blasting devices form ice particulates that are then collected and transported via suction to a blast nozzle for discharge onto a work surface. Since ice particulates are not abrasive in and of themselves, most applications require that the ice particulates be expelled from the nozzle at a very high velocity in order to perform useful work. In general, high particulate velocities are derived from high blast air pressures in the range of about 150 psi to about 200 psi. At these pressures, the blasting devices can quickly suction and propel ice particulates through the blast nozzle with sufficient momentum to do useful work on the work surface.
These prior art suction-driven devices have been used successfully in construction environments, where large air compressors are available, and in manufacturing environments, where dedicated air compressors have been installed. In these cases, sufficient air pressure is available to suction and expel the ice particulates. However, a number of manufacturing environments have air pressure supplies that deliver air pressure in significantly lower amounts, e.g., in the range of about 70 psi to about 100 psi. In these environments, the ice blasting devices that rely on high pressure air to suction ice particulates into the delivery nozzle and onto a work surface do not perform effectively.
Some of the currently known ice blasting devices are pressurized. For example, U.S. Pat. No. 6,001,000 discloses an ice particulate forming device enclosed in a pressure vessel. This and other prior art suction devices are too large and too mechanically complex to be enclosed in a pressure vessel for practical use. Another pressurized ice blasting device currently known (U.S. Pat. No. 5,785,581) produces extremely fine ice particulates formed from the mixing of a cryogenic fluid with atomized water in a nozzle assembly. The use of cryogenic fluids and the small size of such resulting ice particulates are not suitable for many industrial applications. Further, current ice blasting devices are not easily adapted to production operations in which the quantity of ice blasting work varies.
Thus, a need exists for an ice blasting method and apparatus that can provide the economic and environmental advantages that ice blasting permits, and that is capable of being used in manufacturing environments that do not have a high air pressure supply source. Such an apparatus should also be easily modified to accommodate varying levels of ice blasting requirements. The present invention is directed to fulfilling these needs and others as described below.
The invention provides a method and apparatus for producing a stream of ice particulates for use in ice blasting work. The method includes substantially continuously producing ice particulates in an extruder assembly. The extruder assembly includes a pressure vessel within which the ice particulates are formed under elevated pressure. The ice particulates are passed from the pressure vessel to an ice-receiving line containing a fluidizing gas medium from a high pressure supply. The fluidized ice particulates are then discharged from the ice-receiving line through a blast nozzle at atmospheric pressure toward the work surface. A pressure gradient thus exists between the inlet and the discharge of the ice-receiving line, providing a pressure driven flow of particulates through the line and out the nozzle. In one embodiment, the extruder pressure vessel maintains an elevated pressure by receiving pressurized water.
Accordingly, an apparatus for supplying and accelerating ice particulates includes one or more extruder assemblies each having a water input port adapted to receive pressurized water from a supply source and each having an ice discharge opening. The ice-receiving line includes a first end adapted to continuously receive the pressurized fluidizing gas medium from a pressurized air supply source and a second end connected to the blast nozzle. The ice-receiving line is also connected to the extruder assembly ice discharge opening. In one embodiment, the connection is accomplished using an intermediate connection member.
Various alternative embodiments of the present invention apparatus are provided. In one embodiment, at least one extruder assembly is located on top of a movable refrigeration unit. This arrangement allows the apparatus to be easily moved from one location to another without affecting the device or causing work stops. In another embodiment, the apparatus is adapted to a production-line environment in which work objects are moved along a conveyor belt. An upright support frame is located near the conveyor belt and includes an upper shelf. One or more extruder assemblies are located on the upper shelf. An ice-receiving line receives ice particulates from the extruder assemblies and sends the particulates to a blast nozzle that is positioned directly above the conveyor belt. As objects move under the nozzle, useful work is performed as the ice particulates impinge upon the object.